如何在AnyRef上实现同步方法？ [英] How is the synchronized method on AnyRef implemented?

问题描述

在Scala中，AnyRef上有一个同步方法，可让您在扩展AnyRef的任何对象上进行同步。但是，它在AnyRef上是抽象的，我无法通过greping scala源来弄清楚它是如何工作的。似乎可以通过利用Java中的synced关键字来工作。

In Scala, there's a synchronized method on AnyRef which lets you synchronize on any object that extends AnyRef. However, it's abstract on AnyRef, and I couldn't figure out how it worked from grepping the scala source. It seems like it works by exploiting the synchronized keyword in Java. Is that the case?

推荐答案

1） AnyRef.synchronized 是源代码中不存在的魔术方法，但是在每次编译器启动时都会将其注入到编译器的符号表中： Definitions.scala 。顺便说一下，有很多魔术方法和类（ Definitions.scala ）。

1) AnyRef.synchronized is a magic method that doesn't exist in source code, but is injected into the compiler's symbol table on every startup of the compiler: Definitions.scala. There's a number of magic methods and classes, by the way (Definitions.scala).

2）如果方法包装在 this.synchronized ，删除包装，并在内部用 SYNCHRONIZED 标志（ UnCurry.scala ），然后将其映射到JVM的ʻACC_SYNCHRON方法标志 GenASM.scala ）。

2) If a method is wrapped in this.synchronized, the wrapping is dropped, and the method is internally annotated with a SYNCHRONIZED flag (UnCurry.scala), which is then mapped to JVM's `ACC_SYNCHRONIZED method access flag (GenASM.scala).

3）其他对同步的的调用被映射到后端的原始已同步（后端/ ScalaPrimitives） ，后来又降为monitorenter / monitorexit（ GenICode.scala＃1 ， GenICode.scala＃2 ）。

3) Other calls to synchronized are mapped onto the backend's primitive SYNCHRONIZED (backend/ScalaPrimitives.scala), which is later lowered into monitorenter/monitorexit (GenICode.scala #1, GenICode.scala #2).

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